The present invention relates to a member having ultrafine grooves that can be used in a ip displacement control element, motor, relay, switch, shutter, printer head, pump, fan, ink jet printer, and an ink jet printer head using the same.
Recently, in the field of optics and precision processing, a displacement control element capable of adjusting the optical path length or position in the sub-micron order is demanded, and to meet such demand, various actuators are devised including, for example, those utilizing piezoelectric material and others utilizing static electricity.
More lately, in particular, for use in an ink jet printer head, a small-sized actuator is proposed, in which a ceramic green sheet is formed. Air vents forming ink chambers are formed by a die, and by laminating and baking a part thereof as a diaphragm. A piezoelectric drive section is formed on the surface of the actuator (see Japanese Laid-open Patent No. 4-12678).
The structure of an ink jet printer head is as shown in FIG. 7, in which a nozzle plate 23 forming a nozzle 6, a partition wall 22 forming ink chambers 1 or ink passages, and a diaphragm 21 are fabricated of ceramic green sheet. Thereby a head substrate 2 having ink chambers 1 and nozzles 6 and ink passages (not shown) is obtained. An electrode 4a, a piezoelectric element 3, and an electrode 4b are formed on the diaphragm 21 of the head substrate 2.
By applying a voltage between the electrodes 4a and 4b, the piezoelectric element 3 is deformed, and this displacement is transmitted to the ink chambers 1 through the diaphragm 21, so that the ink in the ink chambers 1 can be ejected from the nozzles 6. The ink jet printer head is required to have higher density and higher precision as the product is reduced in size. For example, the width of the partition wall 22 forming the head substrate 2 is demanded to be fabricated in the order of scores of microns.
In the manufacturing process of the ink jet printer head shown in FIG. 7, partition wall 22 is fabricated to form a head substrate 2 by blanking a ceramic green sheet by a die, where the ink chambers 1 and ink passages 6 are formed. Using this process, it is extremely difficult to manufacture the printer head in a such small size yet with high density and high precision. For example, when blanking the green sheet by the die, the sheet may be torn, or the respective position of the different elements with respect to one another may deviate when the diaphragm 21 or the nozzle plate 23 is laminated, thereby making it difficult to manufacture at high density and high precision. Further, it is also difficult and costly to manufacture the die used in such blanking in a small size and at high precision.
The invention, in one or more embodiments, relates to a member for passage having tiny passages of liquid for use in an ink jet head or small-sized pump, and its manufacturing method, and more particularly to an ink jet printer head using the same.
Today, along with the advancement of the multimedia, the demand for personal computers is increasing steadily; and the printer, which is one of the recording media of a personal computer, is required to have higher density and high definition in its performance. In particular, the ink jet system, introduced to replace the existing dot system, has been improved to print more quietly at higher definition and higher density and is now in high demand.
The ink jet system is proposed in various methods, such as the method of discharging ink drops from a nozzle by making use of a piezoelectric material, and the method of generating bubbles in ink by heat and discharging ink drops. In these methods, commonly, the ink is fed into a printer head, the ink is supplied through a passage, and the ink is discharged from an ink discharge port.
Such an ink jet printer head by thermal method is shown in FIG. 8, in which a flat plate 111 has plural partition walls 112, and a substrate 120 is bonded to a member 110 for forming a passage 113 between partition walls 112, thereby covering each passage 113. One end of each passage 113 is a discharge port 114, and the other end communicates with an ink chamber 116 having an ink feed hole 115. Moreover, at a position corresponding to each passage 113 of the substrate 120, a heating element 121 and an electrode 122 for energizing it are disposed.
Moreover, as shown in FIG. 9, when the passage 113 is filled with the ink 130 and the heating element 121 is energized to generate heat, bubbles 132 are generated in the ink 130; and by the force of the expansion of volume of these bubbles 132, ink drops 131 are discharged from the discharge port 113.
Incidentally, higher definition and higher density are demanded in ink jet printers recently. As such, in passage members 110 for composing the ink jet printer head 101, the width of the partition wall 112 and passage 113 are demanded to be as narrow as scores of microns.
To manufacture the passage member 110 having such ultrafine passages 113, various methods have been proposed, including a method of forming a masking in the portion of the partition wall 112 on the flat plate 111, processing grooves as passages 113 by sand blasting, a method of forming partition walls 112 by repeating screen printing on the flat plate 111, a method of applying a photosensitive resin in the portion of the partition walls 112 on the flat plate 111, and forming grooves as passages 113 by photolithography.
However, in the sand-blasting method, since the passages 113 are formed while digging grooves by blowing powder, it is necessary to keep constant the powder blowing force and angle, and it is difficult to process the inner surface of the passages 113 in a specified shape at high precision. In the screen-printing method, it is necessary to print many times, and as a result the partition walls 112 are deformed. In the photolithography method, a slight difference caused by the degree of right angle and depth of the partition walls, due to light illumination angle, time or other condition, can make it difficult to form the passages 113 at high precision. Additionally, in the passage members 110 manufactured using the above-mentioned methods, the inner surface of the passages 113 is not smooth. As a result, the ink flow was disturbed in the passages 113, and fluctuations were likely to occur in the ink discharge volume, discharge pressure, and response. Thus, a method is needed to allow for the formation of the passages 113 at high precision with smooth inner surfaces.
In one or more embodiments, the invention relates to an ink jet printer head used in an ink jet printer. The ink jet printer is a printer for printing by ejecting ink from the head, and it is widely used recently, owing to low noise and high printing speed. The structure of the ink jet printer head is as shown in FIG. 12, in which a head substrate 202 comprises a plurality of ink chambers 201 and ejection ports 206, and piezoelectric elements, where the piezoelectric elements 203 are bonded to positions corresponding to the ink chambers 201. The head substrate 202 includes a plate 223 forming ejection ports 206, a plate 222 forming ink chambers 201, a diaphragm 221, and a piezoelectric element 203 bonded on the diaphragm 221 through a lower electrode 205, whereby a driving electrode 204 is formed thereon.
By deforming the piezoelectric element 203 by applying a voltage between the lower electrode 205 and driving electrode 204, the diaphragm 221 is deflected, and the pressure in the ink chambers 201 is elevated so that the ink may be ejected from the ejection ports 206.
The conventional head substrate 202 and others were made of metal materials, but recently it has been proposed to use ceramics (see Japanese Laid-open Patent No. 6-40030 and Japanese Laid-open Patent No. 6-218929). For example, the head substrate 202 can be formed of ceramics mainly composed of any one of aluminum oxide, magnesium oxide and zirconia oxide. The lower electrode 205, piezoelectric element 203 such as PZT, and driving electrode 204 are formed on the diaphragm 221 to compose the ink jet printer head, so that the reliability may be kept high for a long period of use.
The ceramics-made ink jet printer heads are manufactured by lamination and thermocompression of multiple layers together. For example, green sheets are mainly composed of at least one of aluminum oxide, magnesium oxide and zirconium oxide; plates 222, 223 are fabricated by blanking with a die in the positions corresponding to the ink chambers 201 and ink passages. They are laminated with one green sheet as diaphragm 221 and bonded by thermocompression. The head substrate 202 is fabricated by baking at a temperature of about 1400xc2x0 C., corresponding to the baking temperature of ceramics. Afterwards, on the diaphragm 221 corresponding to each ink chamber 201, metal paste is applied by screen printing as lower electrode 205, and then, for example, a PZT material is formed as piezoelectric element 203 by a thick film forming method, baked at about 1200xc2x0 C., and a driving electrode 204 is formed thereon, thereby producing an ink jet printer head as shown in FIG. 12.
In such ceramics-made ink jet printer head, however, after fabricating the head substrate 202 by integrally baking the plates 222, 223 and diaphragm 221, it is necessary to form and bake the lower electrode 205, piezoelectric element 203 and driving electrode 204 individually on the head substrate 202. This manufacturing process is complicated and expensive, and requires a total of three or more baking steps. Moreover, to adjust to the position of the ink chambers 201, it requires a total of three steps of positioning for the lower electrode 205, piezoelectric element 203 and driving electrode 204. Positioning is difficult, and when these positions are set inaccurately, the expected performance may be greatly diminished.
Furthermore, the disposition of the lower electrode 205, between the piezoelectric element 203 and diaphragm 221, prevents the pressure caused by deformation of the piezoelectric element 203 to be fully transferred to the diaphragm 221, and can therefore lead to a lower driving efficiency. In contrast, in a metal-made ink jet printer head, not only the corrosion resistance is inferior, but also the response of the diaphragm to the piezoelectric element is poor because a bonding material must be placed between the diaphragm and piezoelectric element in order to bond them. It is hence an object of the invention to present an ink jet printer head that can be manufactured easily and is excellent in driving characteristics.
One or more embodiments of the invention are directed to an ink jet printer head displacement control element having ultrafine grooves and a method of manufacturing thereof. The invention is characterized by bonding a partition wall obtained by forming a powder of ceramics, glass, silicon or the like by a molding die with a recess on one side of a flat plate of ceramics, glass, silicon or the like, then integrating and composing a member having ultrafine grooves.
The invention is also characterized by applying a mixture of powders of ceramics, glass, silicon or the like and a binder composed of solvent and organic additive to fill in a molding die having a recess for a partition wall, bonding this mixture to a flat plate of ceramics, glass, silicon or the like, then integrating and manufacturing a member having ultrafine grooves.
The invention is further characterized by forming the flat plate as a diaphragm, comprising a piezoelectric element for driving this diaphragm, an electrode for applying a voltage to the piezoelectric element, and bonding a nozzle plate to form the ultrafine grooves as an ink chamber, thereby composing an ink jet printer head. In one or more embodiments of the invention, a mixture for a partition wall material is applied into a prepared molding die having a recess for a partition wall, and this mixture is bonded and integrated to one side of a flat plate so that the shape of the molding die is directly transferred onto the flat plate. Therefore, when the molding die is preliminarily fabricated at high density and high precision, the partition wall can be easily formed at high density and high precision.
The procedure of bonding and integrating the partition wall and flat plate comprises steps of filling the molding die having the recess with mixture, solidifying tightly on the flat plate, and parting and baking. Alternatively, the procedure of bonding and integrating the partition wall and flat plate comprises the steps of filling the molding die with the mixture, solidifying, parting, contacting with the flat plate, and baking, or the steps of filling the molding die with the mixture, solidifying, parting, baking, and contacting or thermally bonding to the flat plate. Besides, the general glass and ceramics bonding method may be employed.
Another embodiment of the invention is directed to an ink jet printer head passage member and a method of manufacturing thereof. The invention is characterized by bonding a plurality of partition walls obtained by forming powder of ceramics, glass, silicon or the like by a molding die with a recess on one side of a flat plate of ceramics, glass, silicon or the like, integrating by arraying in one direction, and composing passage members having passages between partition walls.
The invention is also characterized by applying a mixture of powders of ceramics, glass, silicon or the like and a binder composed of solvent and organic additive to fill in a molding die having plural recesses for partition walls, bonding this mixture to one side of a flat plate of ceramics, glass, silicon or the like, integrating by arraying in one direction, and thereby manufacturing passage members.
The invention is further characterized by composing an ink jet printer head by covering the passages by bonding a substrate to the upper surface of the partition walls in the passage members, comprising a heating element in each passage, and generating bubbles in the ink in the passages by the heat of the heating elements, thereby discharging the ink.
In the invention, a mixture for partition wall material is filled into a prepared molding die having grooves conforming to the shape of partition walls, and this mixture is bonded and integrated to one side of the flat plates to obtain partition walls, so that the shape of the molding die is directly transferred onto the flat plates. Therefore, when the molding die is preliminarily fabricated at high density and high precision, the partition walls can be easily formed at high density and high precision.
In one ore more embodiments of the invention, the surface of the molding die and the partition walls are smoothly formed to obtain passages having smooth inner surfaces. The procedure of bonding and integrating the partition walls and flat plates comprises steps of filling the molding die having the grooves with mixture, solidifying tightly on the flat plates, and parting and baking, or the steps of filling the molding die with the mixture, solidifying, parting, contacting with the flat plate, and baking, or the steps of filling the molding die with the mixture, solidifying, parting, baking, and contacting or thermally bonding to the flat plate. Besides, the general glass and ceramics bonding method may be employed.
In one or more embodiments, the invention relates to an ink jet printer head comprising plural ink chambers, ejection ports communicating with the ink chambers, and a diaphragm for applying a pressure to the ink chambers, in which the diaphragm is formed of a voltage-withstanding inorganic material, whereby a piezoelectric element is bonded to the diaphragm and a driving electrode is formed on the piezoelectric element.
It is also a feature of the invention that the conductive inorganic material for composing the diaphragm has a volume specific resistance of 1xc3x9710xe2x88x921 xcexa3xcex8cm or less. Moreover, the conductive inorganic material for composing the diaphragm of the invention is composed of any one of conductive ceramics, ceramics or glass having conductive agent, and thermet.
In the ink jet printer head of the invention, the diaphragm is composed of conductive inorganic material, and this diaphragm is used also as the lower electrode, so that the lower electrode is not needed. By applying a driving voltage between the diaphragm and driving electrode, the piezoelectric element can be deformed. Accordingly, the manufacturing process of the lower electrode can be omitted and the manufacturing process can be simplified; moreover, the deformation of the piezoelectric element can be transmitted to the diaphragm efficiently.
Still more, by forming the diaphragm by an inorganic material such as ceramics and glass, the corrosion resistance can be enhanced, and the piezoelectric element can be bonded directly without resort to bonding agent, so that the deformation of the piezoelectric element can be transmitted to the diaphragm more efficiently.